The scope of the Norse language in the British Isles was at times much wider than the Orkney-Shetland area. Vikings coming from Norway and other Nordic countries founded settlements in many corners of Britain and Ireland. Old Norse
had a major influence on the other local tongues,
including English, Scots and Gaelic. However, by the end of the Middle Ages Norse (or its later versions which we can call Norn) was superceded by other languages practically everywhere, except in such remote corners as Orkney and Shetland. Besides these, the last strongholds of Norn in Scotland seem to have been
the Hebrides and Caithness (ON Katanes, North-East Scotland). In
the Hebrides, Norn is believed to have died out in the 1500-1600's
at the latest, replaced by Gaelic, but having left a big number of toponymes and borrowings in the
Celtic language.

At approximately the same time, Norn was devoured by Gaelic and Low Scottish in Caithness. Per Thorsen mentions three possible datings of its decay in his paper "The Third Norn Dialect - That of Caithness" (The Viking Congress, Lerwick, 1950), which is probably the most substantive account on Caithness Norn so far: 15th century (by William Grant, "Scottish National Dictionary", Introduction, § 156), 17th century (by Adolf Noreen, "Altisländische und altnorwegische Grammatik", 4th ed., 20, "Geschichte der nordischen Sprachen", 3rd ed., 2) and 16th century, asserted by Thorsen himself, who cites the following testimony from 1662, which witnesses that the local inhabitants had by that time turned to Gaelic:

The common speech of humble people nowadays is mostly Scottish-Irish, a mixture of the two languages, not markedly one or the other. (Sir John Scott's text to the "Atlas Major" by J. Blaeu, Vol. VI)

One of the main factors which supported the existence
of Caithness Norn during was the constant communication of the locals with Orkney, where its own dialect of Norn
was well entrenched until the 16-17th centuries. However, it did not save Caithness Norn from decay which was
destined to happen, like elsewhere on the mainland.

No written records in Caithness Norn are known to
exist. All that we have to rely upon is the list for Norse words in the Low Scots dialect of Caithness (about 100 instances) collated by Thorsen and published in his article mentioned above. Thorsen mostly resorted to the "English Dialect Dictionary" by Joseph Wright, who,
in his turn, borrowed Caithness words from the manuscript collection of David B. Nicholson,
a native of Wick in Caithness. In several cases Thorsen adds words belonging
generally to Northern Scotland (marked as "N.Sc."), assuming that they also occurred in Caithness.

Unlike Shetlandic and Orcadian material, no grammar features can be worked out
from these forms, and their phonetics fully accord with the main sound pecularities of Norn, especially its Orkney version. The total of Norse words in the local Caithness dialect, including terms common to Scots in general, is estimated
by Thorsen to be "a couple of hundreds".

(b) Terms connected with boats:
lin(n) 'piece of wood put under the keel of a boat to facilitate its being drawn over a loose or sandy beach' < hlunnr
nile 'plug in the water-hole of a boat' < Norw. nygla
noast 'landing-place for boats' < naust 'boat-shed'
anno 'row against the wind to keep the boat from drifting' < andœfa
ouse, in the phrase ouse o'er 'swish over' < ausa 'bale out'